Bioacoustics: Communication and Conservation

Bioacoustics.

Nature has been playing symphonies since long before man discovered ‘music’. They resonate through landscapes and urban cities all around the world to remind us that we aren’t alone.

The variety of sounds, from the rustle of the leaves to the call of the Langurs, produced in different ways, convey their own unique meanings. This has been studied for hundreds of years in order to understand how similar animal communication is to that of us humans.

Many creatures tend to fall prey to those at higher trophic levels. In order to survive, many organisms have their own unique way of communicating, in order to protect themselves from predators. What are these ways of communicating? How do organisms convey ideas using these different methods and sounds? My research has given me knowledge on the various methods of communication animals use, as well as the different types of sounds they produce in order to interact with one another. Much of this involves the use of infrasound, another area I studied in order to understand the various ways in which low frequency communication is used by organisms. Extinction and endangerment are major problems in our world, which is in desperate need of conservation. As I aspire to be a conservationist, I did a lot of research on the various ways in which I can contribute to the environment. The first step I took involved understanding what role recordings play in the conservation of a species, which is explained using a case study of whales.

In order to answer my questions, I collected a number of different resources from the Internet. By using Google and Duke’s online library, I found books, journals, and articles using keywords such as, “bioacoustics” and “acoustics and conservation.” I also found videos and recordings online relating to my topic. By critically engaging with these texts and videos, I have produced my final research paper, answering the questions I have always wondered about.

 

Animal Communication:

The extent of biodiversity in our world means that organisms are able to use a large number of different techniques to communicate with one another. Although my topic focuses on auditory communication, organisms effectively use all their other senses to interact with other animals as well:

  1. Visual
  2. Olfactory
  3. Electrocommunication – fish create an electric field, that if disturbed, convey information
  4. Touch
  5. Seismic – vibrations created by the organism itself are used as signals
  6. Thermal
  7. Autocommunication – the signal is sent by an organism and received back by the same organism after the environment has modified it.

Auditory communication is further classified based on the methods of sound production and the type of sounds produced. When looking at classification based on the method of sound production, we must understand that any movement that causes molecules in the air to vibrate about or causes pressure waves will produce sound. In order to carry out these actions, many organisms have adapted body features. These include:

  1. A Vibrating Membrane that is attached to a muscle. This membrane is like a drum. It is often found in insects and is used to producing mating calls.
  2. A Stridulatory Organ that consists of a ‘scraper’ and a rough surface, present on two different parts of the body. When these are rubbed together they produce a ‘chirp,’ which is higher pitched based on the speed at which the two surfaces are rubbed together. This, again, is found in insects.
  3. A vibrating membrane present in the Larynx of amphibians and mammals, and the Syrinx of birds. The vibration is caused by air pushed up along it by the lungs. The pitch can be changed based on how fast the vibrations are. These vibrations are controlled by muscles, which contract and relax to control the membrane.
  4. A surface, which is struck to produce sounds. This technique is used by a large number of creatures. For example, beavers use their tails to hit the surface of water to create a warning or alarm signal. This is an efficient method of communication, as sound travels very quickly in water.
Beaver striking water.
Beaver Striking the Water With It’s Tail to Produce a Warning Sound.

Why do organisms need to use so many different methods of communication? What would happen if all of organisms of just one species used only a single method to communicate?

One theory could be that animals may not be able to convey all their ideas using just one method of communication. They may require more complex techniques to share more complex messages. Further, I believe that if all organisms used the same technique to exchange information, then the ‘soundscape’ of the organisms, may get ‘saturated’ with sound. The soundscape may get so full of the same sound that messages may be interrupted and organisms may not be able to communicate efficiently. So, by having diversity in the methods of communication, the environment is less full of the same sound, and organisms are able to interact properly.

Another question to consider is what originally influenced the development of these methods of communication. Was it the physiology of the animal, or was it the features of the environment itself? For example, the beaver uses its tail to strike the water and create sound. Did this technique develop because the beaver’s tail was able to create the sound, or because the water was already present in the environment and the beaver could use it to communicate? Although this is a question that may not have a definite answer just yet, it is an interesting one to think about.

When auditory communication is classified based on the type of sound produced, it is usually categorised into the following:

  1. Infrasound – sounds that are below the lower bound of the frequency range that humans can hear.
  2. Audible sound – sounds that humans are able to hear.
  3. Ultrasound – sounds that are above the upper bound of the frequency range that is audible to human.

The most common use of ultrasound is in echolocation, which is carried out by many organisms, including bats, whales, dolphins, and a few species of birds. This process involves the emission of ultrasound from an organism into the environment. The animal waits and ‘listens’ for the echoes after the sound waves reflect off surfaces. The process of echolocation is used to locate and identify objects. Most organisms use it as a form of navigation system, a process known as biosonar. This is used to locate and capture their prey. Many fish, such as herring, are only able to hear up to 4 kHz. However, there are many other fish of the subfamily Alosinae, which are able to hear up to 180 kHz. Porpoises also have one of the highest known frequency ranges, with an upper limit of 160 kHz.

Bat Using Echolocation
Bat Using Echolocation to Detect its Surroundings

Another example of an organism that has the ability to hear ultrasound, is a dog. Humans are not able to hear dog whistles, but the dog themselves are able to do so because the whistle is produced at a very high frequency, that is only audible to dogs. Many insects are also able to hear ultrasound, which they often take advantage of in order to identify incoming bats (their predators) that are using echolocation.

Interestingly, it has been found that a few individuals, who are blind, are also able to use echolocation to help ‘visualise’ their surroundings.

Many animals, including elephants, tigers, whales, giraffes, okapi, and alligators, also use infrasound to communicate with one another. This allows long distance communication, especially in the case of whales, where sound travels more quickly and efficiently in water.

A major contributor to the discovery of the use of infrasound by elephants was Katherine Payne. She has released many videos discussing how she discovered this, and released a book called Silent Thunder: In the Presence of Elephants. In her poptech lecture, Elephant Songs, she talks about how she was observing elephants rumbling and communicating, when she “repeatedly felt a throbbing in the air” (Payne 01:49). She believed that the rumbling was from elephants communicating at a very low frequency. Through further investigation, she discovered that her assumption was true. By recording the elephants and increasing the speed of the recording, she was able to hear sounds at higher frequencies, which allowed her to confirm the result of her investigation.

As part of my research, I used elephant recordings that I found on the Internet, and increased the speed on one copy of the recording and increased the frequency on the other. Although my results were not as clear as those obtained by Payne, there was some evidence of elephant communication taking place at very low frequencies, which was only audible on the modified tracks. These are heard more as rumbles and felt as vibrations, rather than being heard as loud sounds.

Elephants tend to have a very complex and ‘fluid’ social structure, which means that each family or group of elephants tends to be very large and individuals tend to move around freely. These elephant families, consisting mostly of females, tend to merge with other families or groups. Therefore, in order to communicate and locate each other over long distances, elephants tend to use infrasound. These infrasound calls tend to have a frequency of around 21Hz. Each individual call is also unique, so this might help elephants recognize which elephant the infrasound message is coming from. After carrying out a lot of research on the topic, I also believe that the use of infrasound provides the elephants with the private channel of communication that is not understood, heard, or interrupted by other organisms, thereby providing extra protection for the elephants.

A Male African Elephant
A Male African Elephant

Many organisms use infrasound for purposes other than the two mentioned above (communication and protection) as well. An interesting use of infrasound is when a tiger roars. An investigation carried out by bioacoustician Elizabeth von Muggenthaler, showed that the tiger’s infrasound roar has the ability to temporarily paralyze an animal or human. Although it remains a mystery as to how this happens, it is clear that the roar is felt by the organism, but not heard. She carried out the research by playing infrasound and checking whether the tiger would react to it. The reaction by the tiger showed that they were able to hear and therefore produce sounds at very low frequencies. The use of this infrasound roar aids the tiger when it is stalking its prey, as it helps to stall the prey, giving the tiger an opportunity to kill it.

Another fascinating use of infrasound is that by humpback whales and blue whales. They often use sounds ranging from 20 Hz to more than 24 kHz. These whales tend to produce periodically repeating sounds at various frequencies, a phenomenon known as the ‘whale songs’. These have been described by many as the most complex song produced by an animal. The whales, especially humpback whales, tend to produce these songs during the mating season. However, it is not clear how the songs help the whales during the mating process – it may be used to fend off rivals, to attract females, or even to show the whales’ territory. Whales in a particular geographical area tend to sing similar or same songs, whereas those from a different area tend to sing different whale songs. These whale songs in each area are also slowly evolving, with different notes being added to the song. The humpback whales also tend to make two other sounds that are not songs: 1) sounds made during mating and 2) feeding calls. The feeding calls are loud calls made before the whales attack a school of fish, but it is unclear why the whales make this sound. From my study, it seems as though the whales are trying to coordinate their attack on the fish. So by sounding the call, all the whales are able to attack and feed together, thereby making the frenzy more efficient.

Humpback Whales Coordinating an Attack and Feeding on Fish
Humpback Whales Coordinating an Attack and Feeding on Fish

 

Interaction with Humans:

In the 1950’s and the 1960’s, about 50,000 whales were killed each year, until the discovery of something special by Roger Payne. The discovery of the Song of the Humpback Whale. This finding took place when military researcher, Frank Watlington, handed over recordings of submarines and dynamite explosions to Roger Payne, as he could not figure out what the noise in the background was. “These sounds are, with no exception that I can think of, the most evocative, most beautiful sounds made by any animal on Earth,” (May 2014) said Payne.

Payne discovered that the sound the whale was producing was a complex song, as the whale was continuously repeating itself. He realized that he may be able to use this beautiful sound to produce some changes in the whaling industry. In the year 1965, whaling was very severe and humpback whales became endangered. The International Whaling Commission did not allow whaling for a certain period of time, until the whale population increased once more. “Do you make cat food out of composer-poets? I think that’s a crime,” (May 2014) said Payne, as he began to think of ways to make everyone aware of these whale songs. His aim was to integrate the songs into our culture. He distributed the recordings to singers and composers all over the world. A singer crucial to the success of the project was Judy Collins. In her album Whales and Nightingales that was released in 1970, she included the song “Farewell to Tarwathie.” This song, which included actual recordings of whale songs that were given to her, became an instant hit. It spread the idea of whale songs to millions all across the globe.

A couple of years later, after hearing the songs, Greenpeace started their own movement called “Save the Whales,” which was a huge success. The song of the whale seemed to completely change the mindset of people. In this way, recordings of animals can really help in the conservation of the species.

After listening to the recordings, I felt guilt. Guilt for being part of a race that has been destroying these creatures. Guilt for doing nothing to protect these creatures. I am sure this was the same way people felt during the mid 20th century, when the movement was introduced. The songs also give us an opportunity to think about the intelligence of the creatures. As former Greenpeace director Rex Weyler said, “It certainly was a huge factor in convincing us that the whales were an intelligent species here on planet Earth and actually made music, made art, created an aesthetic” (May 2014). Why would one kill organisms that are creating art, and are doing nothing to harm us?

People tend to associate certain actions and ideas with sound. This too could’ve been one of the crucial factors in convincing people to protect whales. An example of this idea can be seen in the movie The Big Lebowski, when the main character is listening to an audio recording of whale sounds, while relaxing and smoking marijuana. Here, the character associates the sounds with the idea of relaxation. In the same way people may associate certain ideas with animal recordings, which makes it more likely that they will refrain from harming such creatures.

By incorporating whale songs into our own songs, we tend to anthropomorphise (ascribe human features to) the whales. Why do we do this? Why do we incorporate them into human culture? By doing so, it feels as though they are now great parts of our lives. It is as if they have a role to play in our lives, whether it involves aiding in music production, or helping us relax. From my research, I also believe that by anthropomorphising the whales, we tend to feel as though the whales are expressing themselves. We tend to feel emotions as if the whales are feeling them too. Although the idea of animals communicating emotion in their sounds is complex, some investigations have been carried out in the field, and documents have been produced, in order to support this idea.

The basic idea of using recordings to convince individuals to help conserve a species can also be used for other animals as well. One example is the recording of tiger roars. Many countries are trying to introduce the recording of tiger roars in order to estimate the tiger population and whether each individual tiger is male or female. The recording is put into computer software that generates spectrograms showing each individual tiger’s roar. Each roar acts as an identity to each individual tiger and can be used to identify it. In the same way, these recordings are being used to estimate animal densities of various creatures all over the world.

Around 5% of the studies carried out on human impact on animal communication show that, effects such as hunting, habitat fragmentation, chemical and noise pollution, “introduced diseases,” “direct human disturbance,” and urbanisation, tend to affect acoustic communication (Laiolo, 2010). Therefore, another way recordings can help with conservation is by helping in identifying how humans have affected the organism’s bioacoustics. By comparing previous and current recordings, changes in the animal’s call can be identified. Although many organisms tend to adapt to their environment in this way, many adaptations may be disadvantageous to the species. This may be because other groups of the species are no longer able to communicate with them, sometimes sexual signs of animals are affected, echolocation of bats and cetaceans can be severely interrupted, habitat loss can affect the way birds select their nesting grounds based on acoustic cues, and noise pollution can also affect social signs of mammals. So through the use of recordings, identification of anthropogenic changes to bioacoustics is made easier. This could help with improvements in conservation of animals, as it is now clear what changes need to be made.

Deforestation in the Amazon
Deforestation in the Amazon

Understanding bioacoustics is very important in a world where wildlife is in desperate need of conservation. By understanding the way organisms communicate, we will soon be able to understand the way organisms feel. Future developments may also see us being able to understand what the organisms are communicating about. By working to achieve our goal of decoding animal communication, efficient interspecies communication may develop as well to some extent, between humans and animals. This will open up a number of opportunities to both animal and man. By making us humans more aware about the way in which organisms live and interact, conservation of various species will improve. Protection provided by the government to the species will improve. People’s view of the organisms will improve. So working towards a positive goal, might give us a better future.

 

 

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